Source measure units (SMU) are used to make precision measurements in many fields, including the testing of semiconductor products. Source measure units force either a voltage or a current and then respectively measure a resulting current or voltage. Existing high voltage amplifier circuits incorporated into an SMU typically use voltage translation circuits to achieve gain from low voltage inputs to high voltage outputs. Existing techniques also make it very difficult to achieve multiple power envelopes as is typically required of a source measurement unit. For example, consider an SMU with 200V, 100 mA and 20V, 1 A. It would be desirable to provide improved amplifier designs that allows for large gain and multiple power envelopes.